https://en.wikipedia.org/wiki/S-300_missile_system
Edit: It looks like Greece ( a NATO member) also has S300 ( How did that happen !!?? ) and Turkey ( also NATO member) has the S400. Not sure if Turkey would allow close examination of their S400 capabilities, even as a NATO member.
The Greek S-300s come from Cyprus (which AFAIK is not a NATO member). They were handed over as a way to resolve the crisis with Turkey about the system itself [1]
> Not sure if Turkey would allow close examination of their S400 capabilities, even as a NATO member.
These days Turkey is a NATO member more de jure than de facto, so who knows. Since the acquisition of S400 caused the expulsion of Turkey from the F-35 program, maybe that could be a bargaining chip to re-enter it in some form ?
It was a compromise after Cyprus got them, but choose not receive them after threats from Turkey (https://en.wikipedia.org/wiki/Cypriot_S-300_crisis)
Greece also has a number of other Russian SAM they bought after the 90s in the lull of the tensions with Russia.
They already do:
https://en.wikipedia.org/wiki/S-300_missile_system#Evaluatio...:
> Evaluation-only operators
> United States – S-300P purchased from Belarus (1994). The system was devoid of electronics.[147] S300V was purchased in Russia officially in the 1990s[clarification needed] (complete set (except for 9S32 GRILL PAN multi-channel guidance radar)).[148]
The systems operated by Greece and inherited by the Soviet Union in the cases of other Nato members are rather old with limited computational resources and limited software developed back in the 80s-90s.
In the case of the S-400 we are probably talking about millions of lines of code developed only years ago and potentially with an update schedule, there is absolutely no way to be sure there is no cutting edge malware that could either infiltrate the rest of the air-defense network, or just ship radar data back to Russia about the signatures of friendly f-35s, that's the real reason the US does not want to sell f-35s to Turkey.
It's one thing to pick up a return from an f-35 on your radar and another to be getting a return and also it's actual position along with IFF information. This data would be invaluable to the Russians and could actually undermine the f-35s stealth performance in a potential conflict in the future.
Plus, if you choose the next-gen AA over the next-gen fighter, there is an implication as to what you'll be shooting at. And since NATO chose the next-gen fighters...
